If you want to use Google Web History and save your browser's history on Google's servers, you generally need to go to this page and select "Enable Web History and install the toolbar". This procedure installs Google Toolbar, a plug-in available only for Internet Explorer and Firefox, and enables the PageRank feature, which displays the ranking of any site you visit while sending the URL to Google in the process.
If you use another browser or if you don't like Google Toolbar, there's an alternative way to send all the web pages you visit to Google: a script that asks Google for the PageRank of any web pages you load in your browser. To install the script you need:
* Greasemonkey, an extension for Firefox. Make sure to restart the browser before trying to add the script.
* Trixie, one of the best Greasemonkey-like plug-ins for Internet Explorer
* SIMBL and GreaseKit for Safari
* no additional software for Opera, but you need to enable the feature from Opera's interface
* Konqueror Userscript for Konqueror
The script is taken from this site, that also adapted it from other scripts. I mirrored the script to an easily-accessible location.
Once you've added the script, you only need to enable Google Web History: go to this page and select "Enable Web History and install the toolbar", but cancel the downloading process (you don't need the toolbar).
This feature only works when you're logged in to your Google Account. To disable it, remove the script from Greasemonkey or from another plug-in you've installed.